1. Field of the Invention
The invention relates to a catalyst temperature estimating device and a catalyst temperature estimating method.
2. Description of the Related Art
There has been devised a catalyst temperature estimating device that estimates a temperature of a catalyst for purifying exhaust gas of an internal combustion engine. For example, a catalyst temperature estimating device according to Japanese Patent Application Publication No. 2003-343242 (JP-A-2003-343242) calculates a steady estimated temperature as a temperature of a catalyst at a time when an internal combustion engine is in a steady operation state, on the basis of a rotational speed of the internal combustion engine and a load applied to the internal combustion engine. The catalyst temperature estimating device according to Japanese Patent Application Publication No. 2003-343242 (JP-A-2003-343242) estimates the temperature of the catalyst by performing a smoothing processing using this calculated steady estimated temperature and a smoothing coefficient determined by the rotational speed and the load.
However, the catalyst temperature estimating device according to Japanese Patent Application Publication No. 2003-343242 (JP-A-2003-343242), may exhibit a large error between the estimated temperature of the catalyst and the actual temperature of the catalyst when the operation state of the internal combustion engine is an acceleration state. Accordingly, the catalyst temperature estimating device according to Japanese Patent Application Publication No. 2003-343242 (JP-A-2003-343242) does not accurately estimate high catalyst temperatures.